JP2015205302A - Seam welding system, seam welding method, and production method of workpiece - Google Patents

Abstract

Seam welding is performed easily with high quality. A seam welding system according to an aspect of an embodiment includes a roller electrode, an electrode moving mechanism (robot arm), a plurality of drive sources (servo motors), and a control unit. A pair of the roller electrodes are provided, and the workpieces are seam-welded by being energized while rotating while sandwiching the workpieces at their peripheral portions. The electrode moving mechanism is provided with the roller electrode, and moves the roller electrode along a weld line of the workpiece. The drive source rotates the joint of the electrode moving mechanism and the roller electrode. The controller controls the amount of rotation of the roller electrode based on a change in torque of the drive source so that a torque acting on the roller electrode is within a preset range. [Selection] Figure 3A

Description

  Embodiments disclosed herein relate to a seam welding system, a seam welding method, and a method for producing a workpiece.

  Conventionally, a seam welding system is known in which a workpiece is held by a robot and seam welding is performed while the workpiece is fed between a pair of roller electrodes (see, for example, Patent Document 1).

  Such a seam welding system includes the pair of roller electrodes having a disk shape, and a motor that is provided for each roller electrode and rotates each roller electrode.

  In the seam welding system, while a workpiece is being fed between the pair of roller electrodes by a robot, the roller electrodes are rotated by a motor while being sandwiched and pressed between the peripheral portions of the roller electrodes, and energized between the roller electrodes. The workpiece is seam welded by the welding current.

  Since the work piece and the roller electrode need only move relatively, in recent years, a roller electrode is attached to the distal end side of the robot arm, and the roller electrode side is connected to the weld line of the work piece by the robot arm. Seam welding systems that move along are also proposed.

JP 2010-158692 A

  However, the above-described conventional technology has room for further improvement in seam welding with high quality and ease.

  Specifically, in the above-described prior art, when the roller electrode is energized, the locus drawn by the roller electrode may not be stable and may deviate from the planned weld line. For this reason, it was inadequate when performing high-quality seam welding on the workpiece.

  In addition, since the locus is not stable as described above, it is necessary to repeat the trial and error to teach the robot, which is complicated.

  One aspect of the embodiments has been made in view of the above, and it is an object to provide a seam welding system, a seam welding method, and a method for producing a workpiece to be welded that can perform seam welding with high quality and ease. And

  A seam welding system according to one aspect of an embodiment includes a roller electrode, an electrode moving mechanism, a plurality of drive sources, and a control unit. A pair of the roller electrodes are provided, and the workpieces are seam-welded by being energized while rotating while sandwiching the workpieces at the peripheral edges of the roller electrodes. The electrode moving mechanism is provided with the roller electrode, and moves the roller electrode along a weld line of the workpiece. The drive source rotates the joint of the electrode moving mechanism and the roller electrode. The controller controls the amount of rotation of the roller electrode based on a change in torque of the drive source so that the torque acting on the roller electrode is within a preset range.

  According to one aspect of the embodiment, seam welding can be easily performed with high quality.

Drawing 1 is a mimetic diagram showing the composition of the seam welding system concerning an embodiment. Drawing 2A is a figure (the 1) showing an outline of a seam welding method concerning an embodiment. Drawing 2B is a figure (the 2) showing an outline of a seam welding method concerning an embodiment. FIG. 2C is a diagram (part 3) illustrating an overview of the seam welding method according to the embodiment. FIG. 2D is a diagram (part 4) illustrating an overview of the seam welding method according to the embodiment. FIG. 2E is a diagram (part 5) illustrating an overview of the seam welding method according to the embodiment. FIG. 2F is a diagram (part 6) illustrating an overview of the seam welding method according to the embodiment. FIG. 2G is a diagram (part 7) illustrating an overview of the seam welding method according to the embodiment. FIG. 2H is a diagram (part 8) illustrating an overview of the seam welding method according to the embodiment. FIG. 3A is a block diagram illustrating a configuration of the seam welding system according to the embodiment. FIG. 3B is a block diagram illustrating an example of the configuration of the correction unit. FIG. 4 is a flowchart illustrating a processing procedure executed by the seam welding system according to the embodiment. FIG. 5 is a block diagram showing a configuration of a seam welding system according to another embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a seam welding system, a seam welding method, and a method for producing an article to be welded will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  In the following description, the case where the seam welding system is a robot system including a robot arm having a seam welding end effector (hereinafter referred to as a “welding gun”) at a tip end portion will be described.

  The robot arm is an example of an electrode moving mechanism that moves a roller electrode included in the welding gun. Here, the electrode moving mechanism can be replaced with another configuration in which the roller electrode is moved by a single-axis driving mechanism. Therefore, the seam welding system is not necessarily a robot system including a robot arm.

  Hereinafter, a workpiece to be seam-welded is described as a “workpiece”.

  Drawing 1 is a mimetic diagram showing the composition of seam welding system 1 concerning an embodiment. FIG. 1 shows a three-dimensional orthogonal coordinate system including the Z axis with the vertical upward direction as the positive direction for easy understanding. Such an orthogonal coordinate system may be shown in other drawings used in the following description.

  In the following, for convenience of explanation, the positional relationship between the respective parts of the robot 10 and the welding gun 20 will be described on the assumption that the turning positions and orientations of the robot 10 and the welding gun 20 are in the state shown in FIG.

  As shown in FIG. 1, the seam welding system 1 includes a robot 10, a welding gun 20, and a control device 30.

  The robot 10 further includes a base 11, a turning base 12, and a robot arm 13. The robot arm 13 further includes a lower arm 13a, an upper arm 13b, a wrist portion 13c, and a flange portion 13d.

  In the following, the installation surface side on which the base 11 of the robot 10 is installed is referred to as “base end side”, and the vicinity of the base end side of each member is referred to as “base end portion”. Further, the flange portion 13d side of the robot 10 is referred to as a “tip side”, and the tip side periphery of each member is referred to as a “tip portion”.

  The base part 11 is a support base fixed to an installation surface such as a floor surface. The turning base 12 is provided on the base 11 so as to be turnable. The lower arm 13 a is provided to be rotatable with respect to the turning base 12.

  The upper arm 13b is rotatably provided with respect to the lower arm 13a. The wrist portion 13c is swingably provided at the distal end portion of the upper arm 13b. The flange portion 13d is provided so as to be rotatable with respect to the wrist portion 13c.

  A welding gun 20 is attached to the flange portion 13d. That is, the robot arm 13 supports the welding gun 20.

  The configuration of the robot 10 will be described in more detail. As shown in FIG. 1, the robot 10 is a so-called vertical articulated type. The turning base 12 is connected to the base portion 11 so as to be turnable around the turning axis S (see arrow 101 in the figure).

  The lower arm 13a is connected to the turning base 12 so that a base end portion thereof is rotatable about an axis L (including a twisted position) substantially perpendicular to the turning axis S (see an arrow 102 in the figure).

  The upper arm 13b is connected to the distal end portion of the lower arm 13a so that the base end portion is rotatable about an axis U substantially parallel to the axis L (see arrow 103 in the figure). Further, the upper arm 13b is provided so as to be rotatable about an axis R that is substantially perpendicular to the axis U (including the twisted position) (see an arrow 104 in the figure).

  The wrist portion 13c is connected to the distal end portion of the upper arm 13b so that the base end portion can swing around an axis B substantially perpendicular to the axis R (see arrow 105 in the figure). The flange portion 13d is connected to the wrist portion 13c so as to be rotatable around an axis T substantially perpendicular to the axis B (see an arrow 106 in the figure).

  In addition, servo motors M1 to M6 are mounted on each joint, which is a movable part of the robot arm 13, and the robot 10 can be variously controlled by controlling the rotation positions of the servo motors M1 to M6. The posture can be changed.

  The welding gun 20 is attached to the flange portion 13d as described above. Next, a specific configuration of the welding gun 20 will be described. For convenience of explanation, FIG. 1 shows the welding gun 20 in a schematic cross-sectional view in which the frame 21 is cut along the XY plane.

  As shown in FIG. 1, the welding gun 20 further includes a frame 21, a movable block 22, a fixed block 23, a cylinder 24, a rail 25, and a pair of roller electrodes 26 and 27.

  The frame 21 supports the movable block 22 and the fixed block 23. The movable block 22 is connected to a cylinder 24 and is supported so as to be slidable along the rail 25 by driving the cylinder 24. The fixed block 23 is fixed to the frame 21.

  The pair of roller electrodes 26 and 27 each have a substantially disk shape when viewed from the X-axis direction in the figure, and one roller electrode 26 is connected to the movable block 22 so as to be rotatable about the axis AXr1. (See arrow 107 in the figure).

  The roller electrode 26 is rotated by a servo motor M7 mounted on the movable block 22. The roller electrode 26 can be slid in the direction of the arrow 108 in the drawing as the movable block 22 slides.

  The other roller electrode 27 is connected to the fixed block 23 so as to be rotatable about the axis AXr2 (see an arrow 109 in the figure). The roller electrode 27 is rotated by a servo motor M8 mounted on the fixed block 23.

  The position and posture of the welding gun 20 configured as described above are changed by the operation of the robot 10 that is an electrode moving mechanism, and the pair of roller electrodes 26 and 27 rotate while sandwiching the workpiece W between the peripheral edges of each other. The workpiece W is seam welded by being energized.

  The energization is performed by flowing a welding current through a power supply cable (not shown) connected to the roller electrode 27 side to an earth cable (not shown) connected to the roller electrode 26 side. Here, the power supply side and the ground side may be reversed.

  Next, the control device 30 will be described. The control device 30 is connected to various devices such as the robot 10 and the welding gun 20 described above so as to be able to transmit information. The connection form may be wired or wireless.

  Here, the control device 30 is a controller that controls the operation of various connected devices, and includes various control devices, arithmetic processing devices, storage devices, and the like.

  Then, the control device 30 executes, for example, the above-described operation control for changing the positions and postures of the robot 10 and the welding gun 20 based on a “job” that is a specific program for operating them. The “job” is registered in advance as teaching information 32 a (described later) in a storage unit 32 (described later) of the control device 30 via an input device (not shown) (for example, a programming pendant).

  The control device 30 generates an operation signal for operating the robot 10 and the welding gun 20 based on the “job” and outputs the operation signal to the robot 10 and the welding gun 20. This operation signal is generated, for example, as a pulse signal to servo motors M1 to M8 mounted on robot 10 and welding gun 20. Details of the configuration of the control device 30 will be described later with reference to FIGS. 3A and 3B.

  Next, the outline of the seam welding method applied to the seam welding system 1 according to the embodiment will be described with reference to FIGS. 2A to 2H. 2A to 2H are views (No. 1) to (No. 8) showing an outline of the seam welding method according to the embodiment.

  Here, in FIG. 2A, a schematic view of the workpiece W in plan view is shown. The code “sp” and the code “ep” indicate “start point” and “end point”, respectively. Hereinafter, description will be given by taking as an example a case where the arcuate line connecting the start point sp and the end point ep is the planned welding line wp.

  First, the operation of the robot 10 and the welding gun 20 is taught such that the pair of roller electrodes 26 and 27 are moved along the planned welding line wp by the robot arm 13 while rotating while sandwiching the workpiece W therebetween.

  Specifically, as shown in FIG. 2B, the roller electrode 26 is slid by driving the cylinder 24 (see the arrow 201 in the figure), and the operation of sandwiching the workpiece W with the roller electrodes 26 and 27 is taught. The Then, the operation of moving the welding gun 20 from the start point sp to the end point ep using the robot arm 13 while rotating the roller electrodes 26 and 27 while sandwiching the workpiece W is taught (see arrow 202 in the figure).

  At this time, as indicated by “no energization (during teaching)” in FIG. 2B, energization between the roller electrodes 26 and 27 is not performed during teaching.

  Thus, the teaching of seam welding is performed so that the locus drawn by the roller electrodes 26 and 27 follows the planned welding line wp while the roller electrodes 26 and 27 are not energized. Further, as shown in FIG. 2C, it is preferable to teach that the thrust of the robot 10 (robot thrust) and the torque (electrode torque) acting on the roller electrodes 26 and 27 at this time are substantially constant. Thereby, the welding gun 20 follows the operation of the robot arm 13 synchronously, and teaching for drawing a stable weld line can be performed.

  However, even if teaching for drawing a stable weld line is performed, energization is performed between the roller electrodes 26 and 27 when seam welding is actually performed, and the conditions are different from those at the time of teaching. It will be. Here, problems in the seam welding method according to the prior art will be described.

  In the seam welding method according to the prior art, as shown in FIG. 2D, the welding gun 20 follows the operation of the robot arm 13 in synchronization and teaches to draw a stable weld line. When the energization is performed between the roller electrodes 26 and 27, the positional relationship between the robot arm 13 and the welding gun 20 may gradually shift.

  FIG. 2E shows changes in robot thrust and electrode torque in such a case. That is, as shown in FIG. 2E, the electrode torque in this case is lower than that when no current is applied, and the robot thrust is higher than that when no current is supplied.

  In other words, the welding gun 20 is delayed from the robot arm 13 and is dragged. Here, due to the synchronization shift between the robot arm 13 and the welding gun 20, stress is generated in the robot arm 13 and the workpiece W, and the deflection of the robot arm 13 or the shift of the workpiece W may be induced in some cases.

  For example, as shown in FIG. 2F, there is a case where the actual welding line wl is shifted inward from the planned welding line wp. Such a phenomenon is considered to be caused by the fact that the roller electrodes 26 and 27 become slippery due to a molten pool or the like generated in the work W when the roller electrodes 26 and 27 are energized.

  Further, since the actual rotation amount of the roller electrodes 26 and 27 is delayed with respect to the operation of the robot arm 13, a deviation is caused between the advance angle AZr (see FIG. 1) of the roller electrodes 26 and 27 and the tangential angle of the planned welding line wp. It also depends on what happens.

  Therefore, in the seam welding method according to the embodiment, even when energization is performed between the roller electrodes 26 and 27, the positional relationship between the robot arm 13 and the welding gun 20 is shown in “no energization (during teaching)” in FIG. It was constructed for the purpose of drawing a stable weld line wl while keeping within a predetermined error with respect to the state of “(scheduled weld line wp)”.

  Specifically, as shown in FIG. 2G, the electrode torque acting on the roller electrodes 26 and 27 when energized is within a range 200 set in advance based on the electrode torque when not energized (during teaching). In addition, the rotational speed (electrode speed) of the roller electrodes 26 and 27 is corrected. Here, the range 200 is set in advance so as to correspond to the above-described predetermined error, but is not limited to the actual welding error being completely within the predetermined error.

  For example, in the seam welding method according to the embodiment, as an example, the electrode speeds of the roller electrodes 26 and 27 are corrected so that the average value of the electrode torque acting on the roller electrodes 26 and 27 is substantially constant within the range 200. The

  The correction of the electrode speed is based on the change in torque of the roller electrodes 26 and 27 based on at least one of the torque changes of the servo motors M1 to M8 which are driving sources for rotating the joints of the robot arm 13 and the roller electrodes 26 and 27, respectively. This is done by controlling the amount of rotation. The torque change is acquired based on a torque command fed back from each of the servo motors M1 to M8, and can be detected without a sensor.

  Further, as shown in FIG. 2G, in correcting the electrode speed, in the seam welding method according to the embodiment, the rotation amount of the roller electrodes 26 and 27 is changed not gradually but gently.

  For example, in the seam welding method according to the embodiment, the rotation amounts of the roller electrodes 26 and 27 are controlled at a low pulse frequency such as several Hz. By gradually changing the rotation amounts of the roller electrodes 26 and 27 in this way, the operation of the welding gun 20 can be gently followed by the operation of the robot 10, so that the welding line wl is corrected with a steep change. Can be prevented. Note that an example of a specific configuration for realizing these will be described later with reference to FIGS. 3A and 3B.

  By taking such measures, in the seam welding method according to the embodiment, even if the roller electrodes 26 and 27 are slippery when energized as shown in FIG. And the welding gun 20 can be made to follow the robot arm 13 in a state close to teaching. Therefore, it can contribute to high quality and easy seam welding.

  Here, returning to the description of the seam welding system 1 according to the embodiment, the block configuration of the seam welding system 1 will be described with reference to FIG. 3A and FIG.

  FIG. 3A is a block diagram illustrating a configuration of the seam welding system 1 according to the embodiment. FIG. 3B is a block diagram illustrating an example of the configuration of the correction unit 31c.

  In FIGS. 3A and 3B, only components necessary for the description of the present embodiment are shown, and descriptions of other components are omitted. For example, the seam welding system 1 includes a power supply device that generates welding power, but the description thereof is omitted here.

  Further, in the description using FIGS. 3A and 3B, description of components that have already been described may be simplified or omitted.

  As illustrated in FIG. 3A, the control device 30 includes a control unit 31 and a storage unit 32. The control unit 31 further includes an inverse kinematics calculation unit 31a, an electrode rotation command unit 31b, and a correction unit 31c.

  The storage unit 32 is a storage device such as a hard disk drive or a nonvolatile memory, and stores teaching information 32a. The teaching information 32 a is information including a program (corresponding to the “job” described above) that defines the operation paths of the robot arm 13 and the welding gun 20. The teaching information 32a includes a predetermined threshold corresponding to the above-described range 200 (see FIG. 2G) and the like.

  Note that all the components of the control device 30 shown in FIG. 3A may not be arranged in the control device 30 alone. For example, the teaching information 32a stored in the storage unit 32 may be stored in an internal memory of the robot 10. Alternatively, the host device of the control device 30 may store the information, and the control device 30 may appropriately acquire from the host device.

  The control unit 31 performs overall control of the control device 30. Specifically, the rotation amounts of the roller electrodes 26 and 27 are controlled based on the torque change of the servo motors M1 to M8 so that the torque acting on the roller electrodes 26 and 27 is within a preset range 200.

  Here, it is assumed that the rotation amounts of the roller electrodes 26 and 27 are controlled based on the torque change of the servo motors M7 and M8 which are driving sources for rotating the roller electrodes 26 and 27.

  The inverse kinematics calculation unit 31a controls the rotational position of each joint of the robot arm 13 based on the operation path of the robot arm 13 registered in advance as the teaching information 32a.

  Specifically, the inverse kinematics calculation unit 31a uses, for example, the coordinate value of the target point on the operation path as the position of the representative point of the welding gun 20, and welds the sliding direction of the roller electrode 26 by the cylinder 24 at this position. As the posture of the gun 20, an operation signal for operating the robot arm 13 is generated by inverse kinematics calculation. Then, such operation signals are output to the servo motors M1 to M6 to operate the robot arm 13.

  Further, the inverse kinematics calculation unit 31a outputs a position command related to the representative point to the electrode rotation command unit 31b.

  The electrode rotation command unit 31b performs a speed calculation at the representative point based on the position command received from the inverse kinematics calculation unit 31a and generates an operation signal for operating the servo motors M7 and M8. Then, the generated operation signals are output to the servo motors M7 and M8 to rotate the roller electrodes 26 and 27, respectively.

  The correction unit 31c acquires torque changes of the servo motors M7 and M8 based on torque commands from the servo motors M7 and M8, and corrects values for correcting the rotation amounts of the roller electrodes 26 and 27 based on the torque changes. Is calculated by feedback control.

  At this time, the correction unit 31c calculates a correction value such that the rotation amounts of the roller electrodes 26 and 27 change gently as described above. Then, the correction value obtained by the calculation is output to the electrode rotation command unit 31b, and the rotation amount of the roller electrodes 26 and 27 is corrected by the electrode rotation command unit 31b.

  Specifically, as illustrated in FIG. 3B, the correction unit 31c is configured to calculate a correction value by, for example, PID control (Proportional Integral Derivative Controller) which is a kind of feedback control.

  In the example shown in FIG. 3B, the correction unit 31c first acquires the average torque from the servo motors M7 and M8, for example, by the average torque acquisition unit 31ca, and passes the low-pass filter 31cb to remove the high-frequency component.

  Then, the correction unit 31c passes the dead band 31cc with respect to the average torque excluding the high frequency component, and calculates an error from the target torque 31cd. The target torque 31cd corresponds to the aforementioned range 200.

  Then, the correction unit 31c obtains an output value from the PID control unit 31ce using the calculated error as an input value, and outputs the output value to the electrode rotation command unit 31b as a correction value via the limiter 31cf.

  Thus, the correction unit 31c calculates a correction value for correcting the rotation amount of the roller electrodes 26 and 27 by feedback control. The correction value is calculated using the low-pass filter 31cb, the dead zone 31cc, the limiter 31cf, and the like based on the average torque as described above. Therefore, the correction unit 31c can obtain the correction value as a value that changes the rotation amount of the roller electrodes 26 and 27 gently rather than steeply.

  As described above, the correction unit 31c of the control unit 31 includes the servo motors M7 and M8 that rotate the roller electrodes 26 and 27 so that the torque acting on the roller electrodes 26 and 27 is within the preset range 200. The process controls the amount of rotation of the roller electrodes 26 and 27 based on at least one of the torque changes.

  Next, the process procedure which the seam welding system 1 which concerns on embodiment performs is demonstrated using FIG. FIG. 4 is a flowchart illustrating a processing procedure executed by the seam welding system 1 according to the embodiment.

  In FIG. 4, it is assumed that teaching for the robot 10 and the welding gun 20 has already been performed and a program in which the operation paths of the robot 10 and the welding gun 20 are defined has been reflected in the teaching information 32a.

  As shown in FIG. 4, first, teaching information 32a is read (step S101). Then, the inverse kinematics calculation unit 31a and the electrode rotation command unit 31b control the rotation amounts of the joints of the robot arm 13 and the roller electrodes 26 and 27 based on the teaching information 32a (step S102).

  Then, the correction unit 31c acquires torque changes of the servo motors M7 and M8 on the roller electrodes 26 and 27 side (step S103). And the correction | amendment part 31c determines whether there exists an error with the time of no electricity supply (step S104).

  Here, when it is determined that there is an error from the non-energized state (step S104, Yes), the correction unit 31c calculates a correction value so that a gradual correction is possible (step S105).

  Then, the electrode rotation command unit 31b corrects the rotation amount of the roller electrodes 26 and 27 with the correction value calculated by the correction unit 31c (step S106).

  If the determination condition in step S104 is not satisfied (step S104, No), the rotation amounts of the roller electrodes 26 and 27 are not corrected (step S107).

  Subsequently, it is determined whether or not the welding is finished (step S108). This determination is made based on, for example, whether or not there is a next program step in the teaching information 32a.

  And when it is not completion | finish of welding (step S108, No), the control part 31 repeats the process from step S101. Moreover, when it is completion | finish of welding (step S108, Yes), a process is complete | finished.

  As described above, the seam welding system according to the embodiment includes a roller electrode, an electrode moving mechanism (robot arm), a plurality of drive sources (servo motors), and a control unit.

  A pair of the roller electrodes are provided, and the workpieces are seam-welded by being energized while rotating while sandwiching the workpieces at their peripheral portions. The electrode moving mechanism is provided with the roller electrode, and moves the roller electrode along a weld line of the workpiece.

  The drive source rotates the joint of the electrode moving mechanism and the roller electrode. The controller controls the amount of rotation of the roller electrode based on a change in torque of the drive source so that a torque acting on the roller electrode is within a preset range.

  Therefore, according to the seam welding system according to the embodiment, seam welding can be easily performed with high quality.

  In the above-described embodiment, the case where the correction unit calculates the correction value based on the average torque of the pair of servo motors that rotate the pair of roller electrodes is described as an example. However, the present invention is not limited to this. For example, an individual correction value for correcting the rotation amount of each roller electrode may be calculated based on the torque change of each servo motor.

  In the above-described embodiment, the case where the rotation amount of the roller electrode is controlled based on the torque change of the servo motor on the roller electrode side is described as an example. However, the torque change of the servo motor on the robot arm side may be used. . That is, the rotation amount of the roller electrode may be controlled based on a torque change of at least one of a plurality of servo motors that rotate each joint of the robot arm.

  Such a case is shown in FIG. 5 as another embodiment. FIG. 5 is a block diagram showing a configuration of a seam welding system 1 ′ according to another embodiment. Since FIG. 5 corresponds to FIG. 3A that has already been shown, the description will mainly focus on the differences from FIG. 3A.

  That is, as shown in FIG. 5, in the seam welding system 1 ′ according to the other embodiment, the correction unit 31 c ′ of the control device 30 ′ changes the torque of at least one of the servo motors M <b> 1 to M <b> 6 on the robot arm 13 side. Configured to get. The correction unit 31c 'is configured to calculate a correction value for correcting the rotation amount of the roller electrodes 26 and 27 based on the acquired torque change on the robot arm 13 side.

  Then, the correction unit 31c 'outputs a correction value obtained by the calculation to the electrode rotation command unit 31b, and causes the electrode rotation command unit 31b to correct the rotation amounts of the roller electrodes 26 and 27. Also in such other embodiments, the torque change is acquired based on the torque command fed back from the servo motors M1 to M6, so that it can be detected without a sensor.

  In each embodiment described above, the seam welding system is a robot system, and the robot is a six-axis single-arm robot. However, the number of axes and the number of arms are not limited. Therefore, for example, a 7-axis robot or a double-arm robot may be used. Further, the seam welding system may not be a robot system.

  Moreover, each embodiment mentioned above is applicable also to the production method of a to-be-welded object. That is, a pair of methods for producing a workpiece to be welded is provided with a pair of electrode moving mechanisms, and a roller electrode for seam welding the workpiece by being energized while rotating while sandwiching the workpiece at the peripheral edge of each other, The step of moving along the weld line of the workpiece using the electrode moving mechanism, and the joint of the electrode moving mechanism and the roller so that the torque acting on the roller electrode is within a preset range. And a step of controlling the amount of rotation of the roller electrode based on a torque change of any of a plurality of drive sources that rotate each of the electrodes. By such a method for producing an object to be welded, for example, an object to be welded that has been hermetically welded with a stable welding line without deviation can be produced.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1, 1 'Seam welding system 10 Robot 11 Base part 12 Turning base 13 Robot arm 13a Lower arm 13b Upper arm 13c Wrist part 13d Flange part 20 Welding gun 21 Frame 22 Movable block 23 Fixed block 24 Cylinder 25 Rail 26, 27 Roller Electrode 30, 30 'Control device 31 Control unit 31a Inverse kinematics calculation unit 31b Electrode rotation command unit 31c, 31c' Correction unit 31ca Average torque acquisition unit 31cb Low pass filter 31cc Dead band 31cd Target torque 31ce PID control unit 31cf Limiter 32 Storage unit 32a Teaching information 200 Range AXr1, AXr2 axis AZr Advancing angle B axis L axis M1 to M8 Servo motor R axis S Swivel axis T axis U axis W Workpiece ep End point sp Start point wl Weld line wp Melting Schedule line

Claims (7)

A pair of roller electrodes that are seam welded to the workpiece by being energized while rotating while sandwiching the workpiece at the periphery of each other;
An electrode moving mechanism to which the roller electrode is attached and moves the roller electrode along a weld line of the workpiece;
A plurality of drive sources for rotating the joints of the electrode moving mechanism and the roller electrodes, respectively.
A seam welding system comprising: a control unit that controls a rotation amount of the roller electrode based on a torque change of the drive source so that a torque acting on the roller electrode falls within a preset range. The controller is
The seam welding system according to claim 1, wherein a rotation amount of the roller electrode is controlled based on a change in torque of the drive source that rotates a joint of the electrode moving mechanism in the drive source. The controller is
The seam welding system according to claim 1, wherein a rotation amount of the roller electrode is controlled based on a torque change of the drive source that rotates the roller electrode of the drive source. The controller is
4. The seam welding system according to claim 1, wherein the rotation amount of the roller electrode is controlled so that an average value of torque acting on each of the pair of roller electrodes becomes substantially constant. 5. The controller is
The seam welding system according to any one of claims 1 to 4, wherein a rotation amount of the roller electrode is gradually changed. A pair of electrode moving mechanisms are provided, and a roller electrode that seams welds the workpiece by rotating and energizing the workpiece while sandwiching the workpiece at the peripheral edges of the electrode moving mechanism. Moving along the welding line of the object,
Based on the torque change of any of a plurality of driving sources that rotate the joint of the electrode moving mechanism and the roller electrode, respectively, so that the torque acting on the roller electrode falls within a preset range. And a step of controlling the amount of rotation. A pair of electrode moving mechanisms are provided, and a roller electrode that seams welds the workpiece by rotating and energizing the workpiece while sandwiching the workpiece at the peripheral edges of the electrode moving mechanism. Moving along the welding line of the object,
Based on the torque change of any of a plurality of driving sources that rotate the joint of the electrode moving mechanism and the roller electrode, respectively, so that the torque acting on the roller electrode falls within a preset range. And a step of controlling the amount of rotation.

Images